Modern wireless communication devices include several blocks or stages that cooperate to achieve a desired functionality. For example, a wireless communication device may include a receiver section having blocks such as an antenna interface, low noise amplifier, mixer, analog to digital converters, a digital signal processor and baseband circuitry coupled thereto. The communication device may also include a transmitter section with several stages or blocks that process a baseband signal for transmission as a radio frequency signal at a desired frequency. A frequency synthesizer may couple to both the receiver section and the transmitter section to control the respective receive and transmit frequencies thereof. The synthesizer itself may include several blocks or stages such as a reference signal oscillator, phase detector, charge pump, low pass filter, voltage controlled oscillator (VCO) and various divider circuits all coupled together according to standard practice in the industry.
It is desirable to be able to monitor the performance of each of the blocks forming a communication device during both the design phase of the communication device and when manufacturing the communication device in the factory. Unfortunately, testing each stage of a communication system can be challenging. When testing the stages of a communication device, it is important that any test apparatus in the communication device not allow spurious radio frequency signals to escape from the device during normal system operation. Moreover, it is desirable that the test apparatus not introduce undesired coupling of spurious radiation between the stages of the communication device. Such coupling could degrade communication device performance and compromise test results.
What is needed is a wireless communication device including an improved test apparatus which addresses the problems discussed above.